Hey Bu5ter,
Only explanation is can offer is that Bosch are very conservative in regards to their flow rates. I have seen my results from a website that sent thier fuel pumps to be tested by indivdual companys. Bosch tests their fuel pumps at 12 volts, whereas most results displayed on the web are at 13.5 volts which would give it more power and more flow. All I really know for sure is that this is the best fuel pump offered by Bosch, and is a top 3 fuel pump for motorsport!
Just remember that at 80 psi all other pumps drop their flow to almost half of the rated flow. Bosch is the only pump that can hold it's pressure AND flow rating. It's a true racing pump for those that require reliable flow.
Hope this helps!
Regards, Scott.